Certain subterranean oil producing wells are formed or completed in formations which contain both oil-producing zones and water-producing zones. Unwanted water production is a major problem in maximizing the hydrocarbon production potential of these wells. Tremendous costs may be incurred from separating and disposing of large amounts of produced water, inhibiting the corrosion of tubulars, replacing tubular equipment downhole, and surface equipment maintenance. Shutting off unwanted water production is a necessary condition to maintaining a productive field. While there is a wide array of treatments available to solve these problems, they all suffer from a number of difficulties, including, but not necessarily limited to, surface mixing and handling problems, etc.
For instance, traditional water shut-off technology with chemicals uses sodium silicate solutions and crosslinked polymers. The silicate solution is typically not compatible with formation waters, since sodium silicate reacts with calcium chloride instantly to generate gel. In this approach, the two solutions may be injected in any order and must be separated by a slug of an inert aqueous spacer liquid. U.S. Pat. No. 4,004,639 provides chemicals to achieve water shut-off in producing wells. It uses base fluid sodium silicate solution and gelling agent ammonium sulfate. Those two solutions are injected and separated by a slug of an inert aqueous spacer liquid. However, these technologies cannot generate uniform gels to plug the porous medium and cannot place the gel deep into the formation. Several staged treatments are also required in pumping the fluids using these techniques.
Crosslinked polymers have also been used to shut off or inhibit water flow. However, crosslinked polymer technology may need separate crosslinkers from the linear polymer fluid separated by a slug of an inert spacer in a form of multi-stage pumping. Crosslinked polymer technology may also use a delayed crosslinking method which may depend on the formation temperature and fluid traveling time in the formation as factors to delay the crosslinking.
Shallow water flow is a serious drilling hazard encountered in several deep water drilling situations including those in the Gulf of Mexico. A number of incidents have occurred in which strong shallow water flows have disrupted drilling operations and added millions of dollars to the cost of a well, or caused a well to be abandoned. It would be desirable if a method and/or composition could be employed to inhibit or prevent shallow water flow in these situations.
Further, improvements are always needed in controlling injection profiles for steam and thermal recovery operations, and to control water injection to improve sweep efficiency during secondary and tertiary recovery of hydrocarbons.
There remains a need to find a chemical system that will simplify the pumping schedule and permit deep penetration into the formation to shut off the water channels in an effective manner and keep oil flow channels open.